Billed for a device returned to Sell Direct

My upgrade was due with Telkom Mobile as I am on the 10 gig for R199 package. I received a call from Sell direct which told me they from Telkom and that my upgrade is due, thinking that this is Telkom , I upgraded to the 7.5gb promo + huawei B593 only to find out that this is sell direct and not Telkom itself. I then cancelled the contract with Sell Direct within the cooling off period and returned their device sealed, which I was told that I will not be billed for this cancellation. I then received a sms from Telkom Mobile saying that I can upgrade to a 10 gig day and 10 gig night with an additional 5 gig for the first three months. I then went into the store to activate this package with Telkom Direct. I was told that I am now on a 10 gig day, 10 gig night with an additional 5 gig for the first three months package. Upon receiving my invoice for the month of March, I am now being billed for my R199 package + R127.79 for a smart internet 7.5GB promo + Huawi B593 device that I have never used and also cancelled and returned to Sell Direct in its sealed condition as Sell Direct requested, ensuring me that no fee will be paid by me for returning this item if still in its sealed box.